Doesn't science frown on hand-waving? It certainly does. That's why, in practice, several radiometric dating methods involving elements with different half-lives are used. One such example (from here):
| Some of the oldest rocks on earth are found in Western Greenland. Because of their great age, they have been especially well studied. The table below gives the ages, in billions of years, from twelve different studies using five different techniques on one particular rock formation in Western Greenland, the Amitsoq gneisses. |
| Technique |
Age Range (billion years) |
| uranium-lead |
3.60±0.05 |
| lead-lead |
3.56±0.10 |
| lead-lead |
3.74±0.12 |
| lead-lead |
3.62±0.13 |
| rubidium-strontium |
3.64±0.06 |
| rubidium-strontium |
3.62±0.14 |
| rubidium-strontium |
3.67±0.09 |
| rubidium-strontium |
3.66±0.10 |
| rubidium-strontium |
3.61±0.22 |
| rubidium-strontium |
3.56±0.14 |
| lutetium-hafnium |
3.55±0.22 |
| samarium-neodymium |
3.56±0.20 |
| (compiled from Dalrymple, 1991) |
|
| Note that scientists give their results with a stated uncertainty. They take into account all the possible errors and give a range within which they are 95% sure that the actual value lies. The top number, 3.60±0.05, refers to the range 3.60+0.05 to 3.60-0.05. The size of this range is every bit as important as the actual number. A number with a small uncertainty range is more accurate than a number with a larger range. For the numbers given above, one can see that all of the ranges overlap and agree between 3.62 and 3.65 billion years as the age of the rock. Several studies also showed that, because of the great ages of these rocks, they have been through several mild metamorphic heating events that disturbed the ages given by potassium-bearing minerals (not listed here). As pointed out earlier, different radiometric dating methods agree with each other most of the time, over many thousands of measurements. Other examples of agreement between a number of different measurements of the same rocks are given in the references below.. |
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If the 'system integrity' of the rock sample had been violated in the distant past (which can indeed happen), these differing methods would show wildly disparate results, not the consistency seen here; as many of the isotopes do not have the same half-life, nor are samples taken from the same region of the rock, nor is the same experimental methodology used in each case; there is no way these differing dating methods could all erroneously collude to the exact same convergence point.
Had you posted raw date, we would see the real variability and 'convergence' would be seen as the manufactured result that it is.
Dalrymple had 3 of 8 samples that tested at 34 billion years old (p 79). How do you 'norm' that?
(Dalrymple, G. B., 1984 How Old is the Earth?: A Reply to ‘Scientific’ Creationism In “Proceedings of the 63rd Annual Meeting of the Pacific Division, American Association for the Advancement of Science” vol. 1, pt. 3, Frank Awbrey and William Thwaites (Eds).)
These guys are making this stuff come out the way they want it to. That much is patently obvious.